BAGHDAD, Sept. 11 -- U.S. Army Spec. Armin J. Cruz Jr. pleaded guilty Saturday to charges of abusing detainees at Abu Ghraib prison and was sentenced by a military judge to eight months in jail for his role in the scandal.

Cruz, a reservist with the 325th Military Intelligence Battalion, was the first soldier from an intelligence unit to face a court-martial for taking part in the mistreatment of detainees in U.S. custody last fall at the notorious prison outside Baghdad. He pleaded guilty to two charges of conspiracy and maltreatment of detainees at the prison.

The military judge, Col. James L. Pohl, also ordered that Cruz, 24, a college student from Plano, Tex., be reduced in rank to private and discharged from the Army for bad conduct.

His civilian attorney, Stephen P. Karns, called Cruz a "war hero . . . who deserves credit for his contribution in liberating Iraq" and said he would appeal the sentence.

Cruz, a first-generation Cuban American whose father was a West Point graduate, was the second soldier sentenced for abuses at the prison but the only military intelligence soldier to be criminally charged.

Seven soldiers from the Army's 372nd Military Police Company have been charged in connection with abuses at Abu Ghraib, which became an international scandal this year after photos emerged showing soldiers beating and sexually humiliating detainees.

Spec. Jeremy C. Sivits, a mechanic assigned to the 372nd, pleaded guilty in May and is serving a one-year prison sentence in Germany.

Staff Sgt. Ivan L. Frederick pleaded guilty to charges of abuse last month and is awaiting a court-martial in late October.

Like Sivits, Cruz agreed to cooperate with Army prosecutors in exchange for a special court-martial, which carries a maximum one-year prison confinement.

Last week the Navy said it had charged four SEALs with abusing detainees at Abu Ghraib. The charges against the four sailors include assault, maltreatment of detainees and making false statements.

Members of the military police unit accused of mistreating detainees at Abu Ghraib have said the abuses were encouraged by intelligence authorities at the prison.

A report issued last month by Army Maj. Gen. George R. Fay found that military intelligence interrogators asked the MPs to use harsh and sometimes illegal tactics. That conclusion contradicted Pentagon statements that the MPs had acted alone in the abuse.

Cruz told the court on Saturday that MPs never participated in interrogations but helped "with setting the conditions."

The charges against Cruz stemmed from a single night in October 2003 when Spec. Roman Krol roused him from bed to find out if Cruz wanted to see how the MPs were dealing with three detainees who had allegedly raped a 15-year-old inmate, according to court testimony.

Cruz said he and Krol helped three accused MPs, Cpl. Charles A. Graner Jr., Staff Sgt. Ivan L. "Chip" Frederick and Spec. Sabrina Harman, force the detainees to crawl naked on the floor and handcuffed them together in sexually humiliating positions.

Cruz said he and Krol also lobbed a soft football at the detainees from the second-story of the cellblock. Cruz said he grew concerned when he saw that one of the detainees' hands had begun to bleed where he was handcuffed.

Cruz said he questioned Graner and Frederick about the detainee's wound and that Graner told him that he "loves this [expletive]."

"This is what he lives for," Cruz said Graner told him. "He can't do this back home."

Cruz hung his head. "There is no way to justify it," he added.

Cruz said he left shortly after that and the next morning reported the incident to his commanders. He heard nothing more until late January, when he received a call from Army criminal investigators, he said. Cruz was not formally charged until July.

In an attempt to explain his behavior that night, Cruz said he did not see the men as three detainees but rather as "three guys who killed two soldiers, injured me, injured my boss."

Cruz was wounded in a mortar attack on the prison on Sept. 20, shortly after he was assigned there. The prison had been under almost daily attacks during the fall, and soldiers and commanders assigned there have described living in constant fear.

Cruz was awarded a Purple Heart for his actions that night. One of his closest friends, Sgt. Travis Friedrich, was one of the two soldiers killed in the attack.

Asked by Pohl if he wanted to punish the detainees for "what happened to your friends," Cruz responded, "Yes, sir."

As Staff Sgt. Frederick J. Krapf testified by telephone about the events that night, Cruz sat at the defense table, wiping tears on the sleeve of his uniform. After Krapf finished, Cruz broke down in sobs and the judge called for a recess. Cruz hunched over and cried for several minutes, while his defense attorneys patted him on the back. He finally left the courtroom, his eyes red and swollen.

When he returned, he took the witness stand and told Pohl that he accepted full responsibility for his actions that night.

"I apologize to the detainees and the soldiers in the service who have to live with the stigma" of the scandal, Cruz said.

Cruz and his attorney said his mental state after the mortar attack may have contributed to his behavior that night.

Cruz testified that he was laughed off when he sought help from his superiors for nightmares and hallucinations.

In a videotape, Cruz's father, Armin J. Cruz, sought to separate his son from the other accused soldiers, saying he "did not enjoy his participation." Some of the photographs from the scandal show smiling MPs posing with abused detainees.

"The Army will not punish Armin more than he will punish himself," Cruz's father said, adding that the abuse "does not define his character."

But the Army prosecutor, Maj. Michael Holley, said that even under stress, Cruz should have known that it was wrong to abuse the detainees that night.

"The accused chose to mock them and degrade them and treat them like animals, not human beings," Holley said. "They were men. They were in our custody."